Radio range



Feb, 29, 1944-. D. G. c. LUCK 2,343,196

RADIO RANGE Original Filed May 5, 1939 s Sheets-Sheet 1 -umenfor David G. C. Liz/c723 cam Gitorneg Feb. 29, 1944. D, G, C, LUCK 2,343,196

RADIO RANGE Original Filed May 5, 1939 3 Sheets- -Sheet 2 Zmvcntor David G. C. Lush;

Gtforncg Patented Feb. 29, 1944 RADIO RANGE David- G. C. Luck, Merchantville, N. 3., assignor to Radio Corporation of America, a corporation ofv Delaware Original application May 5, 1939, Serial No. 272,017. Divided and this application April 1, 1942, Serial No. 437,185

7 Claims.

This inventionis a' division'of my application Serial No. 272,017; filed May 5, 1939, for Radio ranges; now'Patent No. 2,314;795;

This invention relates to radio ranges and more-particularly to means for identifying the courses and quadrants of a four-course radio range.

Radio ranges are transmitting systems which providemeans for establishing partially overlapping directional fields. In the overlapping region, equal signal strengths" designate a desired course. In ranges of the aural type, cornple'm'entary telegraphic signals are generally used. If A and N ("-)are used, the combined'signalsform a single long dash which indicates the desired course.

As long as the pilot of an aircraft is following the radio range signals and knowson which course he is flying, there is no ambiguity. If the pilot becomes lost, although he can hear the range signals, it is only with great difficulty that he can determine in which quadrant of the range he is flying. While it is possible to supplement'the range with a radio direction finder or'to follow'a rather elaborate orientation procedure to'determine the unknown quadrant, it would be preferable to employ an identifying system.

While" quadrant identification meanshave been proposed; the necessary devices are cumbersome and" the system involves complicated circuits; and may" require" auxiliary transmitting channels; It is therefore'one of the objects of "the invention to provide a simple means of quadrant identification for equi-signal radio ranges. It is a further object of theinvention to'provide means supplementing the aural radio range signals for providing visual quadrant identifying signals. An additional object isto provide an indicator" which will show simultaneously the "radio course and its identity.-

The invention will be described by-reference to the accompanyingdrawings in which Figure l is a'schematic diagram of radio range courses; Figures 2a to 2p represent indicationsfor identifying radio range courses; Figures 3a-to 3h represent identifyi-ngand course indications; Figure iis a schematic diagram of the circuits of a radio'range transmitter embodying: the invention; Figure 5 is a schematic circuit diagramof a receiver employing the invention; and Figure 6 a circuit diagramof a modification of the inventiom.

Referring: to Fig.1, the side-band.- field pat ures-of-eight with overlapping portions. One of the figures-of-eight is identified as +N N, the other figure-of-eight is identified as +A A. Lines of equal modulation depth in the I overlapping portions are shown as C1, C2, C3, and

04.. The regions in which one of the radiated patterns has zero intensity are represented as Z1, Z3 and Z2, Z4. For the sake ofa reference point the +N sector has been positioned to correspond to due north, as indicated by the arrow I. At the instant when the modulation phase on one N quadrant is plus, that in the opposite N quadrant is minus. Likewise, when one .A quadrant is plus, the other A quadrant is minus. This characteristic phase of the patterns makes possible a definite identification-of all courses by transmitting a reference phase. This may be done by applying a sub-carrier in the frequency region normally used for speech. 'The subcarrier is modulated in proper phase by the range tone or modulation frequency. If' the signals are properly demodulated by a radio receiver, a reference tone of proper phase may be derived and applied to one winding of a dynamometer having the other winding energized by tone currents corresponding to the radio range modulation. The dynamometer pointer will then defiect to the right if the reference tone and the range tone are of similar phase; the indication Will be to the left if they have opposite phase. The meter indications may be correlated with the AN keying epochs by listening to the signals and by watching the meter deflections. The entire method may be made purely aural, as hereinafter described.

Referring to Fig. 4, the schematic arrangement of the latest type of radio range includes a carrier frequency transmitter 3 which is coupled to a nondirective antenna 5. A sideband frequency transmitter 1 is connected alternately link circuit relay 9 to the northtion frequency of the directional fields which by virtue ofv the-carrier andsideband frequencies may be said to be modulated. In the present ranges, this frequency is 1020 cycles per second. The detector may be energized by a radiation pickup placed suitably in the radiation fields instead of being connected directly.

The currents of modulation frequency are applied to a harmonic generator l3, which, by way of example, provides currents of three times the modulation frequency. These currents are apto the radio frequency phase difference, i. e., the

phase of the modulation is reversed when the initial phase difference between the carrier and sideband waves is changed by 180 degrees. Such 186 degrees change of sidebandphase occurs between lobes of each figure of-eight pattern. Furthermore, the harmonic frequency is transmitted by a reference phase by applying harmonic modulation to the carrier.

The receiver for the radio range transmitter just described is shown schematically in Fig. 5. I'he receiver 2| is connected to a first filter 23 and a second filter 25. The first filter passes the modulation frequency currents which are applied to a phase shifter 21. The phase shifter shifts the phase of the applied currents 90 degrees. The phase shifter output is connected to two of the deflecting elements 29, of a cathode ray tube 3!. The filter output 23 is connected to the other deflecting elements 33. The filter 25 for the third harmonic currents of reference phase is connected to a wave-shaping circuit 35 which converts the applied sine Wave currents to currents of square wave form. These converted currents are applied to'the control electrode '3'! of the cathode ray tube. a

The operation of the receiver is as follows: The radio receiver responds to the combined carrier and sideband currents, the latter being keyed by conventional complementary Morse signals, for example, AN by operation of the link circuit relay. The Morse signals have a modulation frequency corresponding to the difference frequency of the carrier and side bands. The demodulated carrier may be heard'in the telephone receivers 39; The signals corresponding to the difference frequency, after filtering, are applied to the deflecting elements in quadrature phase. The cathode ray is thereby rotated synchronously with the modulation frequency. At the same time, the harmonic frequency currents are applied synchronously to the control grid to bias the ray.

The resultant cathode ray trace is difficult to illustrate because it changes in i the keying rhythm, and therefore may be observed as dots and dashes similar to blinker light telegraph signalling or the operator may observe the flashes and listen to the signals. For purposes of illustration, the solid arcs 4| represent an N or dash dot and the broken arcs 43 represent an A or dot dash (see Fig. 21)). If the receiver is on the Z1 or Z3 courses, no A signals will be received. Therefore, the cathode ray will form a small spot 45 and the N signals will appear as shown in Figs. 7

2a. and 21'. If the receiver is on the Z2 or Z4.

courses (as shown in'Fig's.

The modulator 2e and 2m), the A signals will appear and the small spot represents the absence of N signals. The four patterns, being different, represent and identify four courses on which +N, N, +A or A only are received. Thus four additional or single signal courses are established by a normally four course range.

The patterns corresponding to the four normal or equi-signal courses C1, 0, C3, C4 are ShOWn in Figs. 20, 2g, 2k, 20, respectively. The on-course signals are of equal strength and, therefore, the radius of the solid arc and the broken arc, representing respectively N and A, coincide. As in the case of the off-course patterns, the present oncourse patterns identify the several separate courses.

The conditions for the boundary between the ofi-course quadrants and on-course lines are represented by cathode ray patterns corresponding to 2b, 2d, 2), 2h, 27', 21, Zn, 2p. In these patterns, the radii of the solid are or the radii of the broken arc are greater, respectively, as the N or the A signal predominates. Furthermore, the foregoing eight patterns are all different and are identified with the sectors between the single signal courses and their adjacent equi-signal courses;

, tered at 49 and applied in quadrature phase by connecting a suitably arranged phase shifter 5| to the deflecting elements 53 of a cathode ray tube 55. The grid of the cathode ray tube is keyed by a local oscillator 51, which preferably generates currents of square wave form and the frequency of the range modulation. The several patterns are shown in Figs. 3a to 3h. The sym bols are similar to those previously used in Figs. 2a to 2p. In the present case the lack of synchronism permits the patterns to rotate and the degrees ambiguities'are indicated.

The foregoing receivers employ cathode ray tubes and the cathode ray patterns serve to indicate not only on-course or off-course but also to identify the quadrants and. courses. Some pilots may prefer aural signals, which may be used in connection with either the meter or cathode ray indicator. It is also practical to make the method purely aural by a manual switch, which adds the reference tone algebraically to the range tone in a suitably biased vacuum tube amplifier. The observer will find an increase or decrease of sound dependingupon the relative phases of the two tones; that is, either the A or the N will predominate as a function of the reference phase. a

Thus, the invention has been described as a' or quadrant in which the receiver is operated.

I claim as my invention:

1. A system for identifying the courses and quadrants of a four course simultaneous radio range including means for deriving from the signals of said range an alternating voltage corresponding to the course tone modulation of said range, a voltage responsive indicator device provided with rectangularly disposed deflecting elements, means connected to apply said alternating voltage directly to one of said deflecting elements and through a phase shifting network to another of said deflecting elements, whereby said indicator device displays a substantially circular indication; means for deriving a second alternating voltage of constant phase harmonically related in frequency to said first alternating voltage, and means for applying said second alternating voltage to said indicator device so as to suppress periodically the indication of said device, thereby breaking up said circular indication into distinctive arcuate pattern indicating the courses and quadrants of said range.

2. A system for identifying the courses and quadrants of a radio range providing a special reference phase modulation including means for deriving from the signals of said range an alternating voltage corresponding to the modulation of said range, means for separating the component corresponding to the course tone modulation component of said range from said alternating voltage, a cathode ray tube having rectangularly disposed ray deflecting elements, an intensity control electrode and a fluorescent screen, means for applying said course tone component voltage directly to one of said deflecting elements and through a phase shifting network to another of said deflecting elements, whereby a circular trace is produced on said screen, means for separating the component corresponding to the reference phase modulation component of said range from said alternating voltage, and means for applying said reference phase component voltage to said intensity control electrode of said cathode ray tube whereby said circular trace is broken up into characteristic arcuate patterns indicating the courses and quadrants of said range.

3. The method of identifying the courses and quadrants of a radio range including the steps of deriving from the signals of said range an alternating voltage corresponding to the course tone modulation of said range, deriving from said alternating voltage a second alternating voltage in quadrature phase with said first alternating voltage, deriving a third alternating voltage having a fixed phase and harmonically related in frequency to said first and second alternating voltages, and combining said three alternating voltages to produce indications of distinctive arcuate patterns indentified with the courses and quadrants of said range.

4. A system for identifying the courses and quadrants of a four course simultaneous radio range including a radio receiver with demodulator means for deriving from the signals of said range an alternating voltage corresponding to the course tone modulation of said range, means for deriving a second alternating voltage having a constant phase independent of the phase of said first voltage and related in its frequency to the frequency of said first voltage by substantially an integral number, a voltage responsive indicator device provided with orthogonally related deflecting elements, means for applying said first alternating voltage directly to one of said deflecting elements and through a phase shifting network to another of said deflecting elements, whereby said indicator displays a substantially circular indication, and means for controlling the intensity of the illumination of said indication in response to said second alternating voltage.

5. A system for identifying the courses and quadrants of a radio range, including a radio receiver, filter means connected to said receiver to separate the course tone modulation component from the output thereof, a" cathode ray tube provided with deflection control means and an intensity control circuit, means for applying the course tone output of said filter means to said deflection means so as to produce a substantially circular trace on the screen of said cathode ray tube, means for producing an alternating voltage having a constant phase independent of the phase of said course tone modulation and related in frequency to the frequency of said course tone by substantially an integral number, and means for applying said voltage to said intensity control electrode, whereby said circular trace is broken up into characteristic arcuate patterns indicating the courses and quadrants of said range.

6. A system for identifying the courses and quadrants of a radio range providing a course tone modulation and a special reference phase modulation, including a radio receiver, a filter connected to the output circuit of said receiver and tuned to pass the course tone modulation component of the output thereof, a cathode ray tube provided with orthogonally related deflection elements and intensity control means, connections from said filter directly to one of said deflection control elements, a phase shifter connected to said filter and connections from said phase shifter to another of said deflection control elements, a second filter connected to the output circuit of said receiver and tuned to pass the reference phase tone component of the output thereof, and means for applying the output of said second filter to said intensity control means.

'7. The invention as set forth in claim 6, including wave shape modification means connected between said second filter and said intensity control electrode.

DAVID G. C. LUCK. 

